TWI875492B - Electronic fuse circuit and circuit system using the same - Google Patents

Abstract

The present application discloses an electronic fuse circuit and a circuit system using the same. During startup operation, the circuit system using the electronic fuse circuit of the present application detects an amplitude of the load voltage by a second protection circuit, when the voltage exceeds a set second threshold signal, the electronic fuse circuit is controlled to be turned off; during normal operation, a current of a path where the electronic switch is located is monitored by a first protection circuit to prevent a current of the circuit system from overcurrent. According to the technical solution of the present disclosure, the load can be prevented from damage caused by a failure such as short circuit and electricity leakage of the switch power supply, and the system can be protected from overcurrent.

Description

Electronic fuse circuit and circuit system using the same

The present invention relates to the field of power electronics technology, and more specifically, to an electronic fuse circuit and a circuit system using the same.

In a line system with electrical devices, fuses are indispensable protective devices. Once a traditional fusible fuse is triggered and melted, it needs to be replaced. It is gradually replaced by electronic fuses. Electronic fuses (abbreviated as efuse) are protective devices including electronic switches. They can resume working after the fault is eliminated. By controlling the on and off of the electronic switch, the circuit system can be protected and released.

As shown in Figure 1, a conventional electronic fuse circuit includes an electronic switch and a switch control circuit that controls the on and off of the electronic switch. It is mainly used for overcurrent protection of the line system. Its control scheme is generally to monitor the current size of the path passing through the electronic switch. When the current size reaches the overcurrent protection reference value, the electronic switch is controlled to be turned off. When the current size is less than the overcurrent protection reference value, the electronic switch is controlled to be turned on.

However, in some applications, such as in a circuit system with a switching power supply, as shown in Figure 1, the switching power supply is connected between the electronic fuse and the application load. During the working process of the circuit, such as during the startup process, if the switching power supply leaks or shorts, the load will bear a certain voltage before it is turned on. When the system enters normal operation, the electronic fuse is turned on, and the input electrical signal is converted by the switching power supply and loaded on the load. At this time, there is a risk that the voltage carried by the load is too large, causing damage to the load; in the normal power supply process, if the switching power supply leaks or shorts, the load will also bear too high a voltage, which may cause damage to the load.

Therefore, it is necessary to provide an improved technical solution to overcome the above technical problems existing in the prior art.

In view of this, the purpose of the present invention is to provide an electronic fuse circuit and a circuit system using the same, so as to solve the technical problem of load damage caused by switch power leakage, short circuit and other faults existing in the prior art.

In a first aspect, the present invention provides an electronic fuse circuit for use in a circuit system having a switching power supply, wherein the switching power supply is used to supply power to a load, wherein the electronic switch is coupled to a transmission end of an input power supply and an input end of the switching power supply through a wire, wherein the electronic switch is configured to connect or disconnect the transmission end of the input power supply with the input end of the switching power supply according to a switch control signal; a first protection circuit, wherein the first protection circuit is configured to detect the current of a line in which the electronic switch is located according to an inductive sensing signal and a first threshold value; The first protection signal is obtained by the voltage sensing signal; the second protection circuit obtains the second protection signal according to the voltage sensing signal representing the load voltage and the second threshold signal; the logic circuit is configured to generate a switch control signal for controlling the on and off of the electronic switch according to the first protection signal and the second protection signal, wherein when the current sensing signal reaches the first threshold signal or the voltage sensing signal reaches the second threshold signal, the logic circuit generates a switch control signal for controlling the on and off of the electronic switch.

Preferably, the value of the second threshold signal is set differently in different working states of the circuit system.

Preferably, the value of the second threshold signal in the startup working state is less than the value of the second threshold signal in the normal working state.

Preferably, the first protection circuit is configured such that when the current flow detection signal reaches the first threshold signal, the first protection signal is in a valid state to indicate that the electronic switch is disconnected; the second protection circuit is configured such that when the current flow detection signal reaches the second threshold signal, the second protection signal is in a valid state to indicate that the electronic switch is disconnected.

Preferably, the logic circuit is configured to control the switch control signal to an invalid state for controlling the electronic switch to be turned off if the first protection signal is in an effective state during the operation of the circuit system, or to control the switch control signal to an invalid state for controlling the electronic switch to be turned off if the second protection signal is in an effective state.

Preferably, the logic circuit is configured to control the switch control signal to an invalid state to turn off the electronic switch if the second protection signal is in a valid state during the startup of the circuit system.

Preferably, the first protection circuit includes a first comparison circuit, which receives the current flow detection signal and the first threshold signal to obtain the first protection signal; the second protection circuit includes a second comparison circuit, which receives the current flow detection signal and the second threshold signal to obtain the second protection signal.

Preferably, the logic circuit includes an OR logic and a trigger circuit, the OR logic receives the first protection signal and the second protection signal, and the output end outputs the first logic signal.

The reset end of the trigger circuit receives the first logic signal, the set end receives a switch on/off signal for controlling the conduction of the electronic switch, and the output end outputs a switch on/off control signal for controlling the electronic switch.

Preferably, the logic circuit includes a first trigger circuit, a second trigger circuit and an OR logic, the first trigger circuit has a set end receiving the first protection signal, a reset end receiving a first turn-on signal, and outputs a first logic signal, the second trigger circuit has a set end receiving the second protection signal, a reset end receiving a second turn-on signal, and outputs a second logic signal, the OR logic receives the first logic signal and the second logic signal, and the output end outputs the switch control signal.

In a second aspect, a circuit system having an electronic fuse circuit is provided, wherein the circuit system includes a switching power supply, the switching power supply receives an input power supply voltage through the electronic fuse circuit to convert it into an output electrical signal to drive a load, and the electronic fuse circuit is the above-mentioned electronic fuse circuit.

Preferably, the switching power supply is a step-down switching power supply.

Preferably, the switching power supply is a step-down multi-phase switching power supply, and the multi-phase switching power supply includes a drive control circuit and a multi-phase power stage circuit. When the current sensing signal reaches the first threshold signal or the voltage sensing signal reaches the second threshold signal, the drive control circuit and the multi-phase power stage circuit do not work. The electronic fuse circuit structure and the circuit system using the electronic fuse circuit structure of the present invention are used to detect the load voltage through the second comparison circuit during startup and normal operation. When the voltage exceeds the set second threshold voltage, the electronic fuse circuit is controlled to be disconnected. When the voltage does not reach the set second threshold voltage, the electronic fuse circuit is controlled to be turned on. The current of the electronic switch path is monitored through the first comparison circuit to protect the current of the system line from overcurrent. According to the technical solution of the present invention, the load can be protected from being damaged by short circuit, leakage and other faults of the switch power supply and the system can be protected from overcurrent events.

1: Switch control circuit

11: First protection circuit

12: Second protection circuit

13:Logic circuit

Q: Trigger output terminal

Q1: Electronic switch

_Q : Upper power transistor

Q _lower : lower power transistor

R: Trigger reset terminal

Rcs: differential sampling circuit sampling resistance

S: Trigger set terminal

t1,t2,t3,t4,t5: time

Vcs: current flow detection signal

Vcs1: Current measurement signal representing the current in the circuit where the electronic switch is located

Vcs1’: Current flow detection signal representing the path circuit

Vcs2: Voltage sensing signal representing load voltage

Vg1: switch control signal

Vin: Input voltage

Vo: output voltage

Vocp1: First protection signal

Vocp2: Second protection signal

Vref1: first threshold signal

Vref2: Second threshold signal

V _on : switch on/off signal

_VOpen1 : First opening communication number

_VOpen2 : Second opening number

In order to more completely understand the present invention and its advantages, the following description is provided for reference in conjunction with the drawings, wherein: FIG1 is a circuit diagram of a circuit system of an electronic fuse of the prior art; FIG2 is a circuit diagram of a circuit system including an electronic fuse circuit according to the present invention; FIG3 is a specific circuit diagram of a first embodiment of a switch control circuit according to the present invention; FIG4 is a working waveform diagram according to FIG3; FIG5 is a specific circuit diagram of a second embodiment of a switch control circuit according to the present invention; FIG6 is a schematic diagram of an application scenario of an electronic fuse according to the present invention.

The following is a detailed description of the preferred embodiments of the present invention in conjunction with the drawings, but the present invention is not limited to these embodiments. The present invention covers any substitutions, modifications, equivalent methods and schemes made within the spirit and scope of the present invention.

In order to enable the public to have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, and technicians in this field can fully understand the present invention without the description of these details.

In the following paragraphs, the present invention is described in more detail by way of example with reference to the drawings. It should be noted that the drawings are all simplified and in non-precise proportions, and are only used to conveniently and clearly assist in explaining the embodiments of the present invention.

Reference Figure 2 is a circuit diagram of the circuit system of the electronic fuse according to the present invention, Figure 3 is a specific circuit diagram of the first embodiment of the switch control circuit according to the present invention, and Figure 4 is a working waveform diagram according to Figure 3. The circuit system in the embodiment of the present invention includes a switching power supply, and the switching power supply receives the signal of the input power supply through the electronic fuse circuit. The input power supply can be a DC power supply, and its signal can be a DC voltage signal, which is converted into an output electrical signal to drive the load, and the output signal can be a DC voltage signal.

As shown in the example of FIG. 2 , the electronic fuse circuit includes an electronic switch Q1 and a switch control circuit 1 for controlling the on and off of the electronic switch. The switch control circuit 1 generates a switch control signal Vg1. The electronic switch connects or disconnects the transmission end of the input signal with the input end of the switching power supply through the switch control signal Vg1. The electronic switch Q1 represents a switch or a circuit system including a switch. The electronic switch includes at least one transistor, which can be a metal-oxide-semiconductor field-effect transistor (MOSFET), an insulated gate bipolar transistor (IGBT), a junction field effect transistor (JFET), a bipolar junction transistor (BJT) or other transistors that can achieve the same function.

In the example, the switch control circuit 1 includes a first protection circuit 11, a second protection circuit 12 and a logic circuit 13. The first protection circuit 11 obtains a first protection signal Vocp1 according to an electric current sensing signal Vcs1 representing the line current of the electronic switch and a first threshold signal Vref1; the second protection circuit 12 obtains a second protection signal Vocp2 according to a voltage sensing signal Vcs2 representing the load voltage and a second threshold signal Vref2; the logic circuit 13 is configured to generate a switch control signal Vg1 for controlling the on and off of the electronic switch according to the first protection signal Vocp1 and the second protection signal Vocp2. Here, the current sensing signal Vcs1 can be obtained by using a resistor device such as a resistor Rcs, which represents the current size of the circuit where the electronic switch is located and can be in a certain proportion to the current. The first threshold signal Vref1 is the overcurrent protection threshold of the system; the voltage sensing signal Vcs2 can be obtained by using a voltage detection device such as a voltage divider resistor connected to the output end of the switch power supply or the input end of the load to obtain a signal representing the load voltage. The voltage sensing signal The signal Vcs2 can be in a certain proportion to the load voltage, and the second threshold signal Vref2 is the set overvoltage protection threshold. It should be noted that the value of the second threshold signal is set differently in different working states of the circuit system. The value of the second threshold signal in the startup working state is smaller than the value of the second threshold signal in the normal working state. The size of the second threshold signal can be set to float according to the normal working voltage of the load.

In this example, the first protection circuit is configured so that when the current flow detection signal reaches the first threshold signal, the first protection signal is in a valid state to indicate that the electronic switch is disconnected, and the second protection circuit is configured so that when the current flow detection signal reaches the second threshold signal, the second protection signal is in a valid state to indicate that the electronic switch is disconnected. However, the states of the first protection signal and the second protection signal and the on-off relationship of the electronic switch are not limited to this. This example is for the convenience of demonstrating the invention principle.

For example, the electronic switch can be turned on according to an opening indication signal. For example, after the electronic switch is turned off, a certain delay is performed, and then the opening control is performed according to the control of the clock signal.

Reference FIG3 is a specific circuit diagram of the first embodiment of the switch control circuit according to the present invention. The first protection circuit includes a first comparison circuit, which obtains the first protection signal when receiving the current flow detection signal and the first threshold signal. Here, the first comparison circuit includes a differential sampling circuit and a comparator. The differential sampling circuit samples the voltage at both ends of the resistor Rcs to obtain the current flow detection signal Vcs1' of the characteristic path circuit. The positive input end of the comparator receives Vc s1', the reverse input terminal receives the first threshold signal Vref1, and the output terminal outputs the first protection signal Vocp1. When the voltage sensing signal reaches the first threshold signal, the first protection signal jumps to a high-level valid state; the second protection circuit includes a second comparison circuit, and the second comparison circuit includes a comparator, which receives the voltage sensing signal Vcs2 and the second threshold signal Vref2 to obtain the second protection signal Vocp2.

Continuing to refer to FIG3 , the logic circuit includes an OR logic and a trigger circuit, the trigger circuit includes an RS trigger, the OR logic receives the first protection signal Vocp1 and the second protection signal Vocp2, and the output end outputs the first logic signal, the reset end of the trigger circuit receives the first logic signal, the set end receives a switch on/off signal for controlling the conduction of the electronic switch, and the output end outputs a switch control signal Vg1 for controlling the electronic switch. Here, the working process of FIG. 3 is explained in conjunction with the waveform diagram shown in FIG. 4. For example, during the startup process of the circuit system, at time t1, the first protection circuit detects that the current sensing signal is less than the first threshold signal, and the first protection signal Vocp1 is in a low-level invalid state. The second protection circuit detects that the voltage sensing signal reaches or exceeds the second threshold signal, and the second protection signal Vocp2 is in a high-level invalid state. At this time, the OR gate outputs a high level, the reset terminal of the RS trigger is high, and the output switch is turned on. The off control signal Vg1 is in a low-level invalid state, and the electronic switch is disconnected; until t2, the second protection circuit detects that the voltage sensing signal is lower than the second threshold signal, the second protection signal Vocp2 is in a low-level invalid state, and the gate outputs a low level. After a delay of a period of time, such as at t3, the set end of the RS trigger receives the switch on/off signal Von for controlling the conduction of the electronic _switch , and the switch control signal Vg1 output by the RS trigger is in a high-level valid state, and the electronic switch is turned on. The system enters the normal working state. If at time t4, the first protection circuit detects that the current sensing signal reaches or exceeds the first threshold signal, the first protection signal Vocp1 is in a high-level valid state, the gate outputs a high level, the reset terminal of the RS trigger is high, the output switch control signal Vg1 is in a low-level invalid state, and the electronic switch is disconnected. If during the normal working process of the circuit system, the second protection circuit detects that the voltage sensing signal reaches or exceeds the second threshold signal, the second protection signal Vocp2 becomes a high-level valid state. According to the above process, the switch control signal Vg1 output by the RS trigger is in a low-level invalid state, and the electronic switch is disconnected. Therefore, during the entire working process of the system, the two protection circuits are used to perform good current and voltage event protection.

Reference Figure 5 is a specific circuit diagram of the second embodiment of the switch control circuit according to the present invention; the logic circuit includes a first trigger circuit (first RS trigger), a second trigger circuit (second RS trigger) and an OR-NOT logic, the first RS trigger set end receives the first protection signal Vocp1, the reset end receives the first turn- _on signal Von1 to output the first logic signal, the second RS trigger set end receives the second protection signal Vocp2, the reset end receives the second turn-on signal _Von2 to output the second logic signal, the OR-NOT logic receives the first logic signal and the second logic signal, and the output end outputs the switch control signal Vg1. Here, the first turn-on signal _Von1 and the second turn-on signal _Von2 may be the same signal or different signals. When the second protection circuit detects that the voltage sensing signal reaches or exceeds the second threshold signal, the second protection signal Vocp2 is in a high-level invalid state, the second RS trigger output is high, and after passing through the NOR gate, the switch control signal Vg1 is in a low-level invalid state, and the electronic switch is disconnected. After that, after a delay, the switch control signal Vg1 is controlled to be in a high-level valid state through the second turn-on signal _Vopen2 , and the electronic switch is turned on; similarly, when the first protection circuit detects that the current sensing signal reaches or exceeds the first threshold signal, the first protection signal Vocp1 is in a high-level valid state, the first RS trigger output is high, and after passing through the NOR gate, the switch control signal Vg1 is in a low-level invalid state, and the electronic switch is disconnected. Therefore, when the current sensing signal reaches the first threshold signal or the voltage sensing signal reaches the second threshold signal, the electronic switch is disconnected. Those skilled in the art will know that there are many ways to implement the logic circuit here, such as by combining switches, the purpose of which is to control the switch control signal Vg1 to a low-level invalid state when the first protection signal Vocp1 is in a high-level valid state or the second protection signal Vocp2 is in a high-level valid state, and the electronic switch is disconnected, and the protection effect achieved is the same.

Reference Figure 6 is a schematic diagram of an application scenario of the electronic fuse according to the present invention. The switching power supply is a step-down switching power supply, including two upper and lower transistors and an inductor. If there is leakage _in the transistor of the switching power supply, such as the upper power transistor Q, a voltage will be loaded on the input end of the load. When this voltage is large, during startup or normal operation, the total voltage value exceeds the load-bearing range of the load, which causes damage to the load. The protection scheme of the embodiment of the present invention can be used to monitor the voltage at the load input end to solve this problem.

For example, the switching power supply is a multi-phase step-down switching power supply, and the multi-phase switching power supply includes a drive control circuit and a multi-phase power stage circuit. When the current sensing signal reaches the first threshold signal or the voltage sensing signal reaches the second threshold signal, the drive control circuit and the multi-phase power stage circuit do not work, thereby protecting the load from damage.

Optionally, the electronic fuse circuit can be arranged on the same integrated chip, and it can also be arranged on the same integrated chip with all or part of the circuits in the switching power supply. For example, all or part of the circuits of the switch control unit of the electronic fuse circuit and part of the circuits of the control circuit of the switching power supply can be arranged on the same integrated chip. The embodiments of the present invention are not limited to this.

According to the technical solution of the present invention, during startup or normal operation, the voltage at the load input terminal is detected by the second protection circuit. When the detected signal exceeds the set second threshold signal, the electronic fuse circuit is controlled to be disconnected. When the detected signal does not reach the set second threshold signal, the electronic fuse circuit is controlled to be turned on. While maintaining the original overcurrent protection function of the electronic fuse, overvoltage protection for the load is added. This is very important in some occasions, such as when the load is expensive and difficult to replace, such as the central processing unit (CPU) load. During startup or normal operation, once the voltage applied to the load is found to be too large, the electronic fuse is immediately disconnected through the feedback circuit to prevent damage to the load.

The control methods of the above embodiments can be applied to ordinary flyback converters. The primary side of the flyback converter includes a main transistor. The switch control circuit only controls the main transistor to conduct in the first time period. The control time of the main transistor and the control time of the synchronous rectification transistor are the same as those of the above embodiments and will not be repeated.

The implementation methods described above do not constitute a limitation on the protection scope of the technical solution. Any modifications, equivalent replacements and improvements made within the spirit and principles of the above implementation methods shall be included in the protection scope of the technical solution.

1: Switch control circuit

11: First protection circuit

12: Second protection circuit

13:Logic circuit

Q1: Electronic switch

Rcs: differential sampling circuit sampling resistance

Vcs1: Current measurement signal representing the current in the circuit where the electronic switch is located

Vcs2: Voltage sensing signal representing load voltage

Vg1: switch control signal

Vin: Input voltage

Vo: output voltage

Claims (12)

An electronic fuse circuit is used in a circuit system with a switching power supply, wherein the switching power supply is used to supply power to a load, wherein the electronic switch is coupled to a transmission end of an input power supply and an input end of the switching power supply through a wire, wherein the electronic switch is configured to connect or disconnect the transmission end of the input power supply with the input end of the switching power supply according to a switch control signal; a first protection circuit, which obtains a first protection signal according to an electric current detection signal representing a line current of the electronic switch and a first threshold signal; and a second protection circuit, which obtains a first protection signal according to a first threshold signal representing a load voltage. The voltage sensing signal and the second threshold signal are used to obtain a second protection signal, wherein the second protection circuit is connected to the switch power supply output terminal or the load input terminal to obtain a voltage sensing signal representing the load voltage, and the logic circuit is configured to generate a switch control signal for controlling the on and off of the electronic switch according to the first protection signal and the second protection signal, wherein when the voltage sensing signal reaches the first threshold signal or the voltage sensing signal reaches the second threshold signal, the logic circuit generates a switch control signal for controlling the on and off of the electronic switch. The electronic fuse circuit as described in claim 1, wherein the value of the second threshold signal is set to be different under different working conditions of the circuit system. An electronic fuse circuit as described in claim 1, wherein the value of the second threshold signal in the startup working state is less than the value of the second threshold signal in the normal working state. The electronic fuse circuit as claimed in claim 1, wherein the first protection circuit is configured such that when the current sensing signal reaches the first threshold signal, the first protection signal is in a valid state to indicate that the electronic switch is disconnected; and the second protection circuit is configured such that when the current sensing signal reaches the second threshold signal, the second protection signal is in a valid state to indicate that the electronic switch is disconnected. The electronic fuse circuit as claimed in claim 4, wherein the logic circuit is configured to control the switch control signal to an invalid state for controlling the electronic switch to be turned off if the first protection signal is in an effective state during the operation of the circuit system, or to control the switch control signal to an invalid state for controlling the electronic switch to be turned off if the second protection signal is in an effective state. The electronic fuse circuit as described in claim 4, wherein the logic circuit is configured to control the switch control signal to an invalid state to turn off the electronic switch if the second protection signal is in a valid state during the startup of the circuit system. The electronic fuse circuit as described in claim 1, wherein the first protection circuit includes a first comparison circuit, which receives the current flow detection signal and the first threshold signal to obtain the first protection signal; the second protection circuit includes a second comparison circuit, which receives the current flow detection signal and the second threshold signal to obtain the second protection signal. The electronic fuse circuit as described in claim 7, wherein the logic circuit includes an OR logic and a trigger circuit, the OR logic receives the first protection signal and the second protection signal, the output end outputs the first logic signal, the reset end of the trigger circuit receives the first logic signal, the set end receives a switch on/off signal for controlling the conduction of the electronic switch, and the output end outputs a switch control signal for controlling the electronic switch. The electronic fuse circuit as described in claim 7, wherein the logic circuit includes a first trigger circuit, a second trigger circuit and an OR logic, the first trigger circuit has a set end receiving the first protection signal, a reset end receiving a first turn-on signal, and outputs a first logic signal, the second trigger circuit has a set end receiving the second protection signal, a reset end receiving a second turn-on signal, and outputs a second logic signal, the OR logic receives the first logic signal and the second logic signal, and the output end outputs the switch control signal. A circuit system having an electronic fuse circuit, wherein the circuit system includes a switching power supply, the switching power supply receives an input power supply voltage through the electronic fuse circuit to convert it into an output electrical signal to drive a load, and the electronic fuse circuit is the electronic fuse circuit described in any one of claim items 1 to 9. A circuit system with an electronic fuse circuit as described in claim 10, wherein the switching power supply is a step-down switching power supply. As claimed in claim 11, the circuit system with an electronic fuse circuit, wherein the switching power supply is a step-down multi-phase switching power supply, and the multi-phase switching power supply includes a drive control circuit and a multi-phase power stage circuit, and when the current sensing signal reaches the first threshold signal or the voltage sensing signal reaches the second threshold signal, the drive control circuit and the multi-phase power stage circuit are not working.